The present invention relates to a method and apparatus for affixing a component to a sheet. More particularly, the present invention relates to the field of carrier tape packaging systems in which small electronic components, such as integrated circuit (IC) chips or die, are adhered lengthwise to a tape-like sheet for facilitating handling of the components in various subsequent operations.
Carrier tape packaging systems for electronic components are generally used for facilitating feeding of components in a component pick-and-place assembly line for manufacturing electronic circuit substrates by mounting electronic components on circuit boards.
FIG. 6 shows one example of existing prior art system for retaining unpackaged or bare IC chips within a carrier tape. The carrier tape 110 includes a punched support tape 104 that functions as a leader tape with a plurality of apertures 105 formed at a predetermined pitch, and an adhesive tape 103 adhered to the support tape 104. Bare IC chips 102 are affixed on the adhesive surface 103a of the adhesive tape 103 within each of the cavities formed by the apertures 105.
The process of affixing components on the carrier tape 110 is carried out such that bare IC chips 102 diced from a semiconductor wafer 101 are picked up by a suction nozzle 106 of a transfer robot 107 and transferred one by one onto the adhesive tape 103 of the carrier tape 110 that is fed intermittently and paused at the chip affixing station 108. In order to ensure that chips are stuck to the adhesive tape 103, a table-plate 109 is provided at the chip affixing station 108 for supporting the adhesive tape 103 from below.
The inventors of the present application have tried to apply the above described carrier tape packaging system in the process of forming metal bumps on electrodes of IC chips to be electrically connected to a circuit pattern of a mounting surface, or in the process of leveling such metal bumps to a predetermined height by pressing them. However, it has been found that defective bonds are frequently formed in these processes.
Extensive experiments conducted by the inventors have shown that air pockets exist between the flat surface of IC chips 102 and the adhesive tape 103, and these air pockets hinder the action of ultrasound that is applied for forming bumps by a wire bonding technique utilizing ultrasonic vibration.
It has further been discovered that the formation of such air pockets can be attributable to the method of affixing chips to the tape in which the flat surface of IC chips 102 is placed at one stroke on the adhesive tape 103 that is supported on the table plate 109 in a flat condition, by which air between the chip and tape is entrapped.
Accordingly, an object of the present invention is to provide a method of and an apparatus for affixing components to various forms of sheets without allowing air bubbles to form between the components and the sheets.
In order to achieve the above object, the present invention provides a method of affixing a component on a sheet characterized in that the component is first brought into point or line contact with the sheet in a predetermined point or line contact area, and said point or line contact area between the component and the sheet is then continuously spread until the component is adhered to the sheet.
According to the component affixing method of present invention, instead of face-to-face contact by which air tends to be entrapped, the sheet is at first brought into a point or line contact with the component, so as to avoid formation of air pockets on a sticky surface of the sheet. The point or line contact area between the component and the sheet is then gradually spread thereby pushing away the air that exists between the component and the sheet, whereby the component is smoothly adhered to the sheet without allowing air pockets to be formed. Troubles caused by the air pockets between the component and the sheet can be thus eliminated. The sticky surface or an adhesive layer for affixing the component to the sheet may be provided to one or both of the component or the sheet. The sticky surface should preferably be made of low-tack materials for easy removal of the component from the sheet in subsequent processing.
The initial point contact between the component and the sheet can be made by pressing the sheet with the distal end of a resilient member to the component, and the contact area between the component and the sheet can be spread by pressing the sheet further to the component thereby causing elastic deformation of the resilient member until the component is adhered to the sheet.
The initial line contact between the component and the sheet can be made by pressing the sheet with a circumferential surface of a roller or a flat blade of a spatula to the component, and the contact area between the component and the sheet can be spread by moving the roller or spatula in a direction orthogonal to the direction of line contact between the component and the sheet from one side of the component to the other side thereof until the entire bottom surface of the component is adhered to the sheet.
A support tape that supports the sheet can also be affixed to the sheet similarly to and in association with the process of affixing the component to the sheet without additional or special devices or operations.
The sheet should preferably be in a tape-like form so that a multiplicity of components can be continuously and efficiently affixed lengthwise to the sheet as the sheet is advanced in its lengthwise direction. Tape-like sheet is most suitable for a tape packaging system that is favorably used in continuous supply of components to a predetermined location one by one for various handling and processing.
For implementing the above method of affixing the component to the sheet, the component affixing apparatus of the present invention comprises a component feeding section for supplying components, a feeding mechanism for advancing a tape-like sheet intermittently toward a component affixing position a predetermined distance corresponding to a pitch at which components are affixed to the sheet, a component transfer mechanism for picking up the components fed at the component feeding section and for transferring the components to the component affixing position, and a resilient press member disposed opposite to the component at the component affixing position for pressing the sheet to the component that has been transferred onto the sheet, and a press means for pressing the sheet with a distal end of the resilient press member to the component so that the component and the sheet first make a point contact with each other in a point contact area, and for further pressing the sheet and the component to each other thereby causing the resilient press member to deform elastically so that the point contact area between the component and the sheet spreads toward the periphery of the component whereby the component is adhered to the sheet.
Alternatively, the component affixing apparatus of the present invention may comprise a linear spread means having a linear contact portion disposed opposite to the component at the component affixing position for linearly pressing the sheet to the component that has been transferred onto the sheet, and a press means for pressing the sheet with the linear spread means to the component so that the component and the sheet make a line contact with each other in a line contact area, and for moving the linear spread means in a direction orthogonal to the direction of line contact between the component and the sheet so that the line contact area between the component and the sheet spreads from one side of the component to the other side thereof whereby the component is adhered to the sheet.
With this apparatus a multiplicity of components can be automatically, stably, and efficiently affixed to a tape-like sheet that is fed intermittently in accordance with a predetermined program for controlling each of the means and mechanism of the apparatus.